Organic electroluminescence elements have drawn attention in terms of advantages such as high visibility by self-coloring, excellent, impact resistance for being an entirely solid display unlike a liquid crystal display device, a fast response rate, small influence by a change in temperature, and a wide viewing angle. Incidentally, hereinafter, in some cases, an organic electroluminescence is abbreviated to organic EL.
The configuration of the organic EL element is based on a laminated structure where an organic EL layer is interposed between an anode and a cathode. As a driving method for the organic EL display device including the organic EL element, there are passive matrix driving and active matrix driving, but the active matrix driving is useful in terms that the active matrix driving can be performed at a low voltage in production of a large-sized display. Incidentally, the active matrix driving denotes a method of driving the organic EL display device by forming a circuit such as TFT on a substrate where the organic EL element is formed and driving the organic EL display device by the circuit such as TFTs.
As the organic EL display device, there are a bottom emission type in which light is emitted from a side close to the substrate side in which the organic EL element is formed and a top emission type where light is emitted from a side opposite to the substrate where the organic EL element is formed. Here, in the case of the active matrix driving organic EL display device, in the bottom emission type, there is a problem in that an aperture ratio is limited by the circuit such as TFT formed on the substrate, which is a light emitting surface, and a light emitting efficiency is deteriorated. In contrast, in the top emission type, since light is emitted, from the surface of the side opposite to the substrate, an excellent light emitting efficiency can be obtained in comparison with the bottom emission type. Incidentally, in the case of the top emission type, a transparent electrode layer is used as an electrode layer of the side which becomes the light emitting surface.
A general transparent electrode layer has high resistance in comparison with an electrode layer comprising a metal such as Al or Cu. For this reason, in the organic EL display device having the transparent electrode layer, voltage drop occurs due to the resistance of the transparent electrode layer, and as a result, uniformity of brightness of the organic EL layer is deteriorated, so that a problem of so-called brightness irregularity occurs. In addition, as an area of the transparent electrode layer is increased, the resistance is increased, and thus, the above-described problem of brightness irregularity becomes remarkable in the case of producing a large-sized display.
With respect to the above-described problem, for example, as disclosed in Patent Document 1, there is known a method of suppressing voltage drop by forming auxiliary electrodes having a low resistance value and electrically connecting the auxiliary electrodes to the transparent electrode layer. Here, the auxiliary electrodes are generally formed in a pattern shape by applying an etching process by a wet process after formation of a metal layer. For this reason, in the top-emission organic EL display device, in the case where the auxiliary electrodes are formed after formation of the organic EL layer, there is a problem in that an etchant used for forming the auxiliary electrode is infiltrated into the organic EL layer. Therefore, as disclosed in Patent Documents 2 to 5, there is known a method of forming the auxiliary electrodes before formation of the organic EL layer.
However, if the auxiliary electrodes are formed before formation of the organic EL layer, in the case where the organic EL layer is to be formed on the entire surface or in the case where at least one of the organic layers constituting the organic EL layer is formed on the entire surface, the organic EL layer or the at least one layer of the organic layers is formed on the auxiliary electrodes. For this reason, there is a problem in that connection between the auxiliary electrodes and the transparent electrode layer may be prevented by the organic EL layer or the organic layer on the auxiliary electrodes.
Therefore, in Patent Documents 2 to 3, there is proposed a method of producing the organic EL display device where the organic EL layer on the auxiliary electrodes is removed by a laser beam and the auxiliary electrode and the transparent electrode layer are electrically connected to each other. However, in this case, the organic EL layer removed by the laser beam is scattered, and thus, pixel areas of the organic EL display device are contaminated, so that there is a problem in that display characteristics are deteriorated.
In addition, as a method of solving the above-described problem, for example, in Patent Document 4, there is proposed a method of forming a first electrode having light transmissivity on the entire surfaces of the auxiliary electrodes covered with the organic EL layer before removing the organic EL layer by a laser beam, after that, removing the organic EL layer by the laser beam through the first electrode, and finally, forming a second electrode. However, in this case, although the above-described deterioration in display characteristics can be suppressed, since the first electrode and the second electrode are formed as the transparent electrode layers, there is a problem in that the number of production processes is increased.